文件未显示在cmd提示窗口上

Question

I am fairly new to c++. I am takking a class on intro to structures and objects right now. We finnaly went over files and I got the idea to write a program that encrypts a text file. Just for my own pleasure and knowledge (this is not homework). I havent written the encryption yet, it will be private key because I was told that was easiest and this is my first time trying something like this. Anyway I am just writing the code as functions right now to make sure they work, then will make them into classes later on and expand on the program. So, right now my code will open and write a file. I want to view the file I just wrote in the cmd window before encrypting so I know that I can see the before and after. Heres the code:

//This program will create, store and encrypt a file for sending over the inernet

#include<iostream>
#include<cstdlib>
#include<iomanip>
#include<string>
#include<fstream>
#include"fileSelect.h"

using namespace std;

void openFile(fstream &);
void readFile(fstream &);

int main() {
    //output file stream
    fstream outputStream;
    fstream inputStream;
    string fileName, line;

    openFile(outputStream);
    readFile(inputStream);

    system("pause");
    return 0;
}
//open file Def
void openFile(fstream &fout){
    string fileName;
    char ch;
    cout<<"Enter the name of the file to open: ";
    getline(cin, fileName);
    //try to open the file for writing
    fout.open(fileName.c_str(),ios::out);
    if(fout.fail()){
        cout<<"File, "<<fileName<<" failed to open.\n";
        exit(1);
    }
    cout<<"Enter your message to encrypt. End message with '&':\n";
    cin.get(ch);
    while(ch!='.'){
        fout.put(ch);
        cin.get(ch);
    }
    fout.close();
    return;
}

void readFile(fstream &fin){
    string fileName, line;
    cout<<endl;
    cout<<"Enter the name of the file to open: ";
    getline(cin, fileName);
    //check file is good
    if(fin.fail()){
        cout<<"File "<<fileName<<" failed to open.\n";
        exit(1);
    }

    cout<<"Opening "<<"'"<<fileName<<"'" <<endl;
    //cout<<"Enter the file to open: ";
    //cin>>fileName;
    fin.open(fileName.c_str(),ios::in);
    //readFile(inputStream);
    if(fin){
        //read in data
        getline(fin,line);
        while(fin){
            cout<<line<<endl;
            getline(fin,line);
        }

        fin.close();
    }
    else{
        cout<<"Error displaying file.\n";
    }

    return ;
}

This will compile and run. If openFile() is commented out and the readFile() function is called by itself, the file will read what was written in openFile(). It just wont do it one after the other like I want. It is probably just a simple fix that I am missing but its becoming a bit of a headache now. Any help would be apreciated. Thank you.

Answer 1

When you read the message to encrypt, you don't consume the newline. The newline remains in the input buffer and will cause getline(cin, fileName); to read an empty fileName .

You must first skip the newline after reading the message

string tmp;
getline(cin, tmp);

and then the getline() in readFile will work properly.

OT :

• Your prompt says

   cout<<"Enter your message to encrypt. End message with '&':\\n"; 

  but you test for . and not &

   while(ch!='.'){ 

• You pass an fstream to both openFile and readFile , but open and close the files in these functions. You can use a local variable instead.

  Instead of

   void openFile(fstream &fout){ ... fout.open(fileName.c_str(),ios::out); 

  you write

   void openFile(){ ... fstream fout; fout.open(fileName.c_str(),ios::out); 

  or even shorter

   void openFile(){ ... ofstream fout(fileName.c_str()); 

  Additionally, you must change the declaration and call of openFile() .

  readFile and fin / ifstream work appropriately.